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The Genus Floccularia  

[ Basidiomycota > Agaricales > Agaricaceae . . . ]

by Michael Kuo

In North America, this small group of species is apparently limited to western locations, from the Rocky Mountains to the West Coast, where they are saprobes that act like mycorrhizal mushrooms, since they're generally found in the vicinity of trees. The mushrooms feature Tricholoma-like stature, attached gills, a white spore print, and partial veils that leave a ring or a sheath on the stem. These features also apply to several species of Tricholoma (for example Tricholoma murrillianum), but microscopic examination of spores reveals a crucial difference: species of Floccularia have amyloid spores, while the spores of Tricholoma species are inamyloid.

Identification of Floccularia species relies on macroscopic features like colors and the scaliness or "fibrilloseness" of the cap surface. Under the microscope the North American species do not appear to manifest substantial differences.

The genus Floccularia has not been subjected to contemporary, DNA-based study, and the position of Floccularia within the Agaricales order has not been reliably determined—nor have the individual species been examined. So if you are an enterprising mycology graduate student, Floccularia is a doctoral thesis waiting to happen! The mushrooms are gorgeous and charismatic, and collected with enough frequency that there are plenty of specimens available in public herbaria. And, just between you and me, the species concepts are outdated and shaky-at-best, so you are likely to upend everything and create quite a Floccularia stir with your work! Just don't forget us little people when you're rich and famous.


Floccularia luteovirens

Floccularia fusca

Floccularia fusca

Key to 6 Floccularias in North America  

1.Yellow shades present on the gills or cap, at least by maturity.

1.Yellow shades absent from gills and cap in all stages of development.

2.Young cap bright yellow and prominently scaly.

2.Young cap dull yellow or brownish; bald or with appressed fibrils but not prominently scaly.

3.Edge of the cap fairly bright yellow at maturity; hyphae in pileipellis not constricted at septa.

3.Edge of the cap not bright yellow at maturity; hyphae in pileipellis often constricted at septa (illustration).

4.Cap grayish to grayish brown, at least over the center.

4.Cap whitish.

5.Young cap prominently scaly.
Floccularia straminea var. americana f. alba

5.Young cap smooth or with appressed fibers.
Floccularia albolanaripes f. alba


Cripps, C. L., V. S. Evenson & M. Kuo (2016). The essential guide to Rocky Mountain mushrooms by habitat. Urbana: University of Illinois Press. 260 pp.

Lange, C. (2018). Floccularia Pouzar. In Knudsen, H. & J. Vesterholt, eds. Funga Nordica: Agaricoid, boletoid, clavarioid, cyphelloid and gastroid genera. Copenhagen: Nordsvamp. 626–627.

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Mitchel, D. H. & Smith, A. H. (1978). Notes on Colorado fungi III: New and interesting mushrooms from the aspen zone. Mycologia 70: 1040–1063.

Thiers, H. D. & Sundberg, W. J. (1976). Armillaria (Tricholomataceae, Agaricales) in the western United States including a new species from California. Madroño 23: 448–453.

Volk, T. J. & Burdsall, H. H. (1995). A nomenclatural study of Armillaria and Armillariella species (Basidiomycotina, Tricholomataceae). Synopsis Fungorum 8.

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Kuo, M. (2020, February). The genus Floccularia. Retrieved from the MushroomExpert.Com Web site:

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